Brodmann area 15

Area 15 was defined by Brodmann in the guenon monkey, but he found no equivalent structure in humans. However, functional imaging experiments have found structures that may be homologous.

Anatomy

Gross Anatomy

Area 15 is located in the part of the insula nearest the temporal lobe and part of the anterior temporal lobe facing the insula. It is buried in the Sylvian Fissure and thus not visible on the surface of the brain without dissection.

Cytoarchitecture

Area 15, like all Brodmann areas, is defined on the basis of cytoarchitecture of the region of cortex. The cortex in area 15 is thinner than in the rest of the insula and temporal lobe. The molecular layer (I) is unusually wide; the external granular layer (II) and the external pyramidal layer (III) are less dense, and the internal granular layer (IV) is totally absent, so that the medium-sized pyramidal cells of layer III and the internal pyramidal layer (V) merge with a few isolated granular cells scattered at their boundary. The multiform layer (VI) divides into a more densely cellular outer sublayer (VIa) and a less dense inner sublayer (VIb). As in Brodmann area 14, the sublayer VIb merges with the adjacent claustrum. The cells in all of layer VI form tangential rows similar to the formation seen in area 10 and area 11.

Existence in Humans

Brodmann Area 15 is one of the areas that was not found in humans; however, at least one research group has found an area in approximately the correct anatomical location with similar functions.